Brass left by expert in jewellery (8)
I believe the answer is:
necklace
'jewellery' is the definition.
(necklace is a kind of jewellery)
'brass left by expert' is the wordplay.
'brass' becomes 'neck' (I've seen this in other clues).
'left' becomes 'l' (common abbreviation).
'by' says to put letters next to each other.
'expert' becomes 'ace' (ace is a kind of expert**).
'neck'+'l'+'ace'='NECKLACE'
'in' acts as a link.
(Other definitions for necklace that I've seen before include "Ornamental string" , "decorative band" , "Ornamental feature" , "String of beads, perhaps" , "Decorative chain" .)